Knauf dry screed: pros and cons

To make the floor even, without a single flaw and defect, professional builders use different methods and techniques in their work. However, more and more new products appear on the construction market every day, with the help of which almost everyone can cope with the task of imperfect floors..

The dry floor technique proposed by Knauf allows you to create high-quality floor coverings in the shortest possible time, without unnecessary material and physical costs..

Knauf dry screed – the right solution for creating the perfect floor covering.

Peculiarities

Knauf-superpol is German quality, reliability and durability. The technology is a multi-layer construction of a floor made of gypsum fiber panels (GWP). The leveling layer is a dry moisture-resistant backfill in the form of expanded clay sand, the dimensions of which are carefully selected and controlled. Expanded clay backfill allows you to remove almost all the disadvantages of floor slabs (distortions, slopes, etc.) and create a perfectly flat base surface for future flooring. Gypsum panels are quick and easy to install, and a minimum of waste is left in the process.

The popularity of Knauf dry screed floors explains them high-class technical characteristics. Floors created with this technology give owners a feeling of coolness in summer, and, on the contrary, warm in winter. They do not emit extraneous sounds, do not creak, do not crackle, guarantee perfect sound insulation.

Knauf dry screed floor coverings have a fine, even surface, aesthetically pleasing and durable.

Knauf subfloors are installed during:

  • laying all kinds of floor coverings in multi-storey high-rise buildings, office and commercial premises, in cottages, country houses, hotels;
  • restoration of structures built in the 50-60s of the last century or buildings with wooden partitions;
  • if the room is always cold and it is not possible to make a concrete screed;
  • underfloor heating in buildings with wooden floors;
  • with minimal time to create a subfloor.

With a dry floor of the Knauf trademark, various defects and distortions of the base can be eliminated. The unique technology “dry screed” can be used for such types of coatings as parquet, tiles, laminate, linoleum, however, the folds of linoleum and parquet must be glued with a PVA solution or something similar.

The advantages of Knauf flooring include:

  • the formation of a perfectly flat base of the floor, which can withstand a load of 500 kg / m2, in the spot version – 200 kg / m2;
  • high refractoriness;
  • hypoallergenic (dry filling does not cause allergic attacks in asthmatics and people prone to allergic reactions);
  • excellent sound insulation, no squeaks and crackles occur when walking, no cracks appear throughout the entire service life;
  • optimal thermal properties;
  • the possibility of installing gypsum plasterboards;
  • operational capabilities (you can move along the dry backfill immediately after its installation);
  • quick installation;
  • the ability to create a floor in turn in different rooms without losing a single height level;
  • lack of “wet” construction processes;
  • the possibility of laying any coating on the top layer of a dry floor: porcelain stoneware, tiles, laminate, parquet boards, linoleum.

But, despite the obvious advantages, Knauf dry backfill has disadvantages:

  • low moisture resistance. If moisture for any reason gets on the floor covering, you will have to open the entire structure to dry it, and in some cases a complete replacement of the covering takes place. Therefore, a dry screed should not be used in the bathroom and in the kitchen, where there are temperature drops and the level of humidity is quite often increased, if warm water floors are created, in unheated or poorly heated and basements;
  • high degree of dustiness when backfilling expanded clay crumbs. During construction work, you must wear a respirator;
  • higher cost compared to other types of flooring;
  • high sub-floor height. It is not always appropriate to use the dry screed method, especially when the ceiling height in the room is not sufficient to do the job..

Composition

Knauf floors are called differently: dry screed, dry backfill, superfloors. However, all this is a combination of different materials that are used when installing a rough screed..

A dry screed is a prefabricated composition of the following elements:

  • Vapor barrier. A thick PVC construction film that is laid on the floor slab to prevent unwanted moisture penetration. If you use it on wooden floors, you can avoid accidental spillage of expanded clay granules into the gaps between the boards..
  • Edge tape. It is used for additional sound insulation. Absorbs the sounds of human footsteps and other possible noises. Lay it over the entire area of ​​the room between the screed and all the walls.
  • Dry backfill. Most often, expanded clay sand is used with a fraction size of no more than 5 mm. For backfilling, materials such as perlite, quartz sand, fine-grained slag, etc. are also used. The dry mixture evens out the base of the floor, smooths out all irregularities, pits and slopes. The minimum thickness of the dry backfill layer must be at least two centimeters.

  • United among themselves moisture resistant gypsum fiber sheets size 120x60x2 cm. Produced in Knauf factories and used in subfloor systems. When creating a dry screed, they are lined with backfill, coated with PVA building glue and fixed with self-tapping screws.
  • PVA glue. A white solution with a specific odor is used for gluing Knauf floor elements (GVL). Glue is applied to the seams of adjacent elements, after which the sheets are additionally fixed with self-tapping screws. Floor elements turn into a solid and solid base.
  • Self-tapping screws. Special fasteners for gypsum fiber with a head and an external thread. Used when laying dry backfill to fasten additional floor elements together. Together with PVA glue, they provide high-quality and reliable fixation of floor elements to create a solid base, ready for laying the final layer of flooring.

Consumption

To understand how much dry screed is needed per 1 m2, it is necessary to take into account the following parameters:

  • squaring the room;
  • the selected height of the backfill mixture;
  • sizes and options for placement of building materials.

To carry out installation work, you will also have to perform a calculation:

  • the volume of expanded clay chips (sand);
  • the number of gypsum boards;
  • damper tape length;
  • linear footage of PVC film;
  • the number of profile rails;
  • number of screws;
  • displacement of PVA glue.

First of all, you need to find out how much PVC film required for waterproofing will be needed. We must not forget that, according to the rules, it should overlap, by about 20-30 cm, and also “go” on each wall (the length depends on the height of the bulk floor. The film is most often sold in rolls of 1.5 m wide. Usually it is double and if expand it, then the entire width will be 3 m.

Not every screed is laid using beacons. If the room is small, you can do without additional markers.. But thanks to these elements, it is much easier to level the backfill layer..

Profile bars are produced in lengths of 3 m, therefore, in a room of a typical multi-storey building, they are placed across the room, at a distance of one meter from each other. With this arrangement, the number of profiles is determined based on the length of the room with an extension in one extreme rail.

To find out how much GVL is needed, you need to calculate the floor area and, focusing on the dimensions of the slabs, determine their required number.

To calculate the consumption of expanded clay chips, you need to decide in advance what thickness of the backfill will be used, while taking the average as a basis, which is especially important when there are drops at the base of the floor. The average thickness is determined by the maximum and minimum point of its height. The volume of expanded clay is further established by multiplying the quadrature of the room where the work is carried out and the thickness of the backfill layer. It is not always possible to make a perfectly accurate calculation, therefore experts advise buying expanded clay with a small stock.

The size of the damper tape must match the perimeter of the room, and you do not need to skip the width of the doorways.

It is better to buy a slightly longer tape in case it accidentally breaks or other unforeseen situations occur..

The calculation of the amount of PVA glue is quite simple. The manufacturer indicates that 50 grams of glue is needed per square meter of the room, therefore, this number must be multiplied by the area of ​​the room and as a result, the amount of the required product is obtained..

According to building codes, up to 10 self-tapping screws must be installed in each gypsum fiber sheet, but not less than 6. Thus, it is very easy to calculate the total number of fasteners..

Minimum thickness

The thickness of the backfill of the dry mix for the floor depends on the quality of the surface of the floor itself (the number of irregularities and other defects, the magnitude of the slope), as well as on the presence and characteristics of utilities.

As a rule, the layer thickness ranges from 30-50 mm..

Laying technology

Knauf brand dry screed is performed in several stages:

  • Preparatory work. All the old finish is completely removed, after which the surface is inspected for flaws. If deficiencies are found, they must be filled with a cement-sand mortar in a ratio of 1 to 3.
  • Waterproofing. It is necessary to estimate the amount of work to be done, depending on the set humidity in the room. The minimum that will have to be done is to cover the entire floor with a film, fix the seams with tape, and then lay a damper tape around the perimeter of the room (if it does not have a glued side, you can grab it using a special construction tape).

  • Installation of beacons and profiles. Without these elements, it is difficult to lay the backfill, especially in a large area. The slats are laid on the floor (no matter where the work is done: in the kitchen, in the living room, bedroom, office or in the factory), aligned with the building level and the rule.
  • Backfilling of voids with expanded clay. To reduce the number of movements on the surface of the new screed, the expanded clay fraction should be filled in from the side opposite to the door. Such work must be carried out both with a wooden floor and with other types of flooring..
  • Leveling the screed. This process is performed by a rule. If beacons are installed in advance, the alignment is very fast..
  • Floor laying. According to the filling principle, it is carried out from the far corner of the room to the front door. Knauf sheets are fixed with self-tapping screws.

The main difference between dry and wet backfill is the timing of the installation.

If in the “wet” version all the stages of work need to be done in one day, then in the “dry” version the work can be divided into several days, take a break or even pause for an indefinite amount of time. An exception is the finishing part of the installation, the manufacturer advises to carry it out. in one day. This will protect the dry backfill from moisture ingress..

Reviews

Basically, the products of the Knauf company, and in this case the dry screed, have positive reviews. The advantages of consumers include: quick work execution, absence of dirt during installation, good sound insulation and relative heat of the coating. I also like the fact that you can walk on the floor immediately after its installation and it looks monolithic compared to a concrete screed..

However, there are also negative statements. Buyers note that if the floor was accidentally damaged (a small amount of water got into the structure), mold may form under the floor system. And this means that you will have to dismantle the entire coating or install a new floor, and this is fraught with high financial costs..

They also say that if linoleum is lined on the floor, then heavy cabinet furniture with legs can push through the GVL plates, and the sharp heels of women’s shoes can leave visible dents on the coating, which will spoil the aesthetic appeal of the floor covering. In a flood the screed dries for a very long time, and there is no certainty that it will dry out at all.

You will learn how strong the floors made by the Knauf dry screed method are in the next video..

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